A burst of wet weather could have helped to kill off mammoths and other large herbivores, by transforming much of the world's grasslands into bogs and forests and depriving megafauna of food.

What it could have looked like when humans and megafauna lived together: a giant macropod Procoptodon goliah in the foreground, while Thylacinus cynocephalus hunts for prey nearby. A herd of Zygomaturus can be see on the lake edge of the ancient Willandra system.
Illustration by Laurie Beirne January 11, 2017

If Earth were like a human body, large animals might be its arteries, moving nutrients from where they’re abundant to where they’re needed. Currently the planet has large regions where life is limited…